1. Field of the Invention
The present invention relates to a drive device, preferably for lifting columns for height-adjustable tables, and comprising an endless chain running over first and second chain wheels with a first chain run and a second chain run between the two chain wheels, wherein at least one chain run may be connected with a movable element in the structure in which the drive device is to be incorporated. The invention moreover relates to a lifting column containing such a drive device.
2. The Prior Art
SE 513 249, MPI Teknik AB, discloses a lifting column having three members whose movement is based on an endless chain in a closed tubular profile. Two rods protruding from the respective ends of the tubular profile are secured to the chain. The two rods are secured to the outer member and the inner member, respectively, of the column, while the closed tubular profile with the chain is secured in the central member. The telescopic movement of the column is caused by a linear actuator, which is secured with its one end to a base plate in the outer member and to the top of the tubular profile with the chain. The structure performs well as far as it goes, but it requires a column of a considerable cross-section to accommodate the actuator and the tubular member with the chain arranged side by side. In addition, the movement of the column is limited to the length of stroke of the actuator. If a great travel is desired in the column, it requires an actuator having a great length of stroke, but then the mounting height of the column becomes large, as the length of stroke of the actuator is directly related to its length—great length of stroke, long actuator. The structure is not particularly easy to mount either, just as the course of force is not optimum, resulting in inexpedient moment loads.
The object of the invention is to obviate the problems outlined above.